Little research has focused on personality disorders in older adults. It is clear, however, that personality disorders can be quite debilitating in late life. Currently, there are no age appropriate diagnostic criteria specifically designed to evaluate personality disorders in older adults. Many of the criteria put forth by the Diagnostic and Statistical Manual-IV focus on a younger social and occupational context. The absence of age-appropriate criteria forces researchers and clinicians to draw conclusions based on existing criteria, which are likely inadequate: Three studies will be conducted to develop a set of diagnostic criteria that is appropriate to use with older adults. Study 1 is designed to determine which of the current criteria provide age-biased estimates of the presence of personality pathology. Study 2 is designed to revise the current criteria for use with older adults and establish the reliability and validity of those new criteria in a community sample. Study 3 is intended to demonstrate the utility of the new criteria by replicating the findings of study 2 in a clinical sample. The findings from these studies hopefully will lead to better assessment criteria for adults and further understanding of how personality pathology manifests itself in older adults.